Electrostatic clamps or chucks (ESCs) are often utilized in the semiconductor industry for clamping workpieces or substrates during plasma-based or vacuum-based semiconductor processes such as ion implantation, etching, chemical vapor deposition (CVD), etc. Clamping capabilities of the ESCs, as well as workpiece temperature control, have proven to be quite valuable in processing semiconductor substrates or wafers, such as silicon wafers. A typical ESC, for example, comprises a dielectric layer positioned over a conductive electrode or backing plate, wherein the semiconductor wafer is placed on a surface of the ESC (e.g., the wafer is placed on a surface of the dielectric layer). During semiconductor processing (e.g., ion implantation), a clamping voltage is typically applied between the wafer and the electrode, wherein the wafer is clamped against the chuck surface by electrostatic forces.
At colder temperatures, the mismatch of coefficients of thermal expansion (CTE) between the dielectric layer and the backing plate can cause significant deformation in the surface of the ESC. Among other problems, this deformation leads to potential leakage of backside gas, and further reduces wafer handling reliability.
Therefore, a need exists in the art for an improved electrostatic clamp wherein deformation of the clamp is minimized over a predetermined temperature range.